Re: [Rd] anova and intercept
Yes, that works fine too. It likely depends on what you want to show and to whom. The audience might be ready to see the equivalence between t-tests and anova(lm(...)) but not yet prepared for variance components. - Peter > On 27 Dec 2022, at 18:55 , Greg Snow <538...@gmail.com> wrote: > > Why compute the differences manually when `aov` can do paired > comparisons on this data as is: > > summary(aov(extra ~ factor(group) + Error(ID), data=sleep )) > > gives the same F and P values > > On Tue, Dec 27, 2022 at 3:32 AM Gabor Grothendieck > wrote: >> >> Good idea. >> >> On Mon, Dec 26, 2022 at 12:59 PM peter dalgaard wrote: >>> >>> My usual advice on getting nonstandard F tests out of anova() is to fit the >>> models explicitly and compare. >>> >>> So how about this? >>> >>> fit1 <- lm(diff(extra,10) ~ 1, sleep) >>> fit0 <- update(fit1, ~ -1) >>> anova(fit0, fit1) >>> >>> -pd >>> On 26 Dec 2022, at 13:49 , Gabor Grothendieck wrote: Suppose we want to perform a paired test using the sleep data frame with anova in R. Then this works and gives the same p value as t.test(extra ~ group, sleep, paired = TRUE, var.equal = TRUE) ones <- rep(1, 10) anova(lm(diff(extra, 10) ~ ones + 0, sleep) This gives output but does not give an F test at all. ones <- rep(1, 10) anova(lm(diff(extra, 10) ~ 1, sleep) Maybe there should be some way to force an F test to be produced for the intercept in anova for consistency with t.test so that the second code can be used. -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel >>> >>> -- >>> Peter Dalgaard, Professor, >>> Center for Statistics, Copenhagen Business School >>> Solbjerg Plads 3, 2000 Frederiksberg, Denmark >>> Phone: (+45)38153501 >>> Office: A 4.23 >>> Email: pd@cbs.dk Priv: pda...@gmail.com >>> >> >> >> -- >> Statistics & Software Consulting >> GKX Group, GKX Associates Inc. >> tel: 1-877-GKX-GROUP >> email: ggrothendieck at gmail.com >> >> __ >> R-devel@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel > > > > -- > Gregory (Greg) L. Snow Ph.D. > 538...@gmail.com -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd@cbs.dk Priv: pda...@gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] anova and intercept
Why compute the differences manually when `aov` can do paired comparisons on this data as is: summary(aov(extra ~ factor(group) + Error(ID), data=sleep )) gives the same F and P values On Tue, Dec 27, 2022 at 3:32 AM Gabor Grothendieck wrote: > > Good idea. > > On Mon, Dec 26, 2022 at 12:59 PM peter dalgaard wrote: > > > > My usual advice on getting nonstandard F tests out of anova() is to fit the > > models explicitly and compare. > > > > So how about this? > > > > fit1 <- lm(diff(extra,10) ~ 1, sleep) > > fit0 <- update(fit1, ~ -1) > > anova(fit0, fit1) > > > > -pd > > > > > On 26 Dec 2022, at 13:49 , Gabor Grothendieck > > > wrote: > > > > > > Suppose we want to perform a paired test using the sleep data frame > > > with anova in R. Then this works and gives the same p value as > > > t.test(extra ~ group, sleep, paired = TRUE, var.equal = TRUE) > > > > > > ones <- rep(1, 10) > > > anova(lm(diff(extra, 10) ~ ones + 0, sleep) > > > > > > This gives output but does not give an F test at all. > > > > > > ones <- rep(1, 10) > > > anova(lm(diff(extra, 10) ~ 1, sleep) > > > > > > Maybe there should be some way to force an F test to be produced for > > > the intercept in anova for consistency with t.test so that the second > > > code can be used. > > > > > > > > > -- > > > Statistics & Software Consulting > > > GKX Group, GKX Associates Inc. > > > tel: 1-877-GKX-GROUP > > > email: ggrothendieck at gmail.com > > > > > > __ > > > R-devel@r-project.org mailing list > > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > -- > > Peter Dalgaard, Professor, > > Center for Statistics, Copenhagen Business School > > Solbjerg Plads 3, 2000 Frederiksberg, Denmark > > Phone: (+45)38153501 > > Office: A 4.23 > > Email: pd@cbs.dk Priv: pda...@gmail.com > > > > > -- > Statistics & Software Consulting > GKX Group, GKX Associates Inc. > tel: 1-877-GKX-GROUP > email: ggrothendieck at gmail.com > > __ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] anova and intercept
Good idea. On Mon, Dec 26, 2022 at 12:59 PM peter dalgaard wrote: > > My usual advice on getting nonstandard F tests out of anova() is to fit the > models explicitly and compare. > > So how about this? > > fit1 <- lm(diff(extra,10) ~ 1, sleep) > fit0 <- update(fit1, ~ -1) > anova(fit0, fit1) > > -pd > > > On 26 Dec 2022, at 13:49 , Gabor Grothendieck > > wrote: > > > > Suppose we want to perform a paired test using the sleep data frame > > with anova in R. Then this works and gives the same p value as > > t.test(extra ~ group, sleep, paired = TRUE, var.equal = TRUE) > > > > ones <- rep(1, 10) > > anova(lm(diff(extra, 10) ~ ones + 0, sleep) > > > > This gives output but does not give an F test at all. > > > > ones <- rep(1, 10) > > anova(lm(diff(extra, 10) ~ 1, sleep) > > > > Maybe there should be some way to force an F test to be produced for > > the intercept in anova for consistency with t.test so that the second > > code can be used. > > > > > > -- > > Statistics & Software Consulting > > GKX Group, GKX Associates Inc. > > tel: 1-877-GKX-GROUP > > email: ggrothendieck at gmail.com > > > > __ > > R-devel@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > -- > Peter Dalgaard, Professor, > Center for Statistics, Copenhagen Business School > Solbjerg Plads 3, 2000 Frederiksberg, Denmark > Phone: (+45)38153501 > Office: A 4.23 > Email: pd@cbs.dk Priv: pda...@gmail.com > -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] anova and intercept
My usual advice on getting nonstandard F tests out of anova() is to fit the models explicitly and compare. So how about this? fit1 <- lm(diff(extra,10) ~ 1, sleep) fit0 <- update(fit1, ~ -1) anova(fit0, fit1) -pd > On 26 Dec 2022, at 13:49 , Gabor Grothendieck wrote: > > Suppose we want to perform a paired test using the sleep data frame > with anova in R. Then this works and gives the same p value as > t.test(extra ~ group, sleep, paired = TRUE, var.equal = TRUE) > > ones <- rep(1, 10) > anova(lm(diff(extra, 10) ~ ones + 0, sleep) > > This gives output but does not give an F test at all. > > ones <- rep(1, 10) > anova(lm(diff(extra, 10) ~ 1, sleep) > > Maybe there should be some way to force an F test to be produced for > the intercept in anova for consistency with t.test so that the second > code can be used. > > > -- > Statistics & Software Consulting > GKX Group, GKX Associates Inc. > tel: 1-877-GKX-GROUP > email: ggrothendieck at gmail.com > > __ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd@cbs.dk Priv: pda...@gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] anova and intercept
Suppose we want to perform a paired test using the sleep data frame with anova in R. Then this works and gives the same p value as t.test(extra ~ group, sleep, paired = TRUE, var.equal = TRUE) ones <- rep(1, 10) anova(lm(diff(extra, 10) ~ ones + 0, sleep) This gives output but does not give an F test at all. ones <- rep(1, 10) anova(lm(diff(extra, 10) ~ 1, sleep) Maybe there should be some way to force an F test to be produced for the intercept in anova for consistency with t.test so that the second code can be used. -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
